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Prometheus binary format metrics data structures for Python client libraries

Project description

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prometheus_metrics_proto

The prometheus_metrics_proto package provides Prometheus Protobuf data structures and a set of helper functions to assist generating Prometheus Protocol Buffer format metrics and serializing them in preparation for network transfer.

The collection of metrics and the management of Summary Quantiles and Histogram Buckets are outside the scope of functionality provided by this package.

An example of a project using prometheus_metrics_proto is aioprometheus which uses it within the the BinaryFormatter.

The Protocol Buffer specification used by prometheus_metrics_proto was obtained from the Prometheus [client model[(https://github.com/prometheus/client_model/blob/master/metrics.proto) repo.

Install

$ pip install prometheus_metrics_proto

Example

The prometheus_metrics_proto package provides helper functions to assist with generating Prometheus metrics objects.

The example below shows how these functions can be used to construct metrics and encode them into a format suitable to send to Prometheus server in a response.

#!/usr/bin/env python
"""
This script demonstrates the high level helper functions used to assist
creating various metrics kinds as well as how to encode the metrics into
a form that can be sent to Prometheus server.
"""

import prometheus_metrics_proto as pmp


def main():

    # Define some labels that we want added to all metrics. These labels are
    # independent of the instance labels that define a metric as unique.
    # These could be used to add hostname, app name, etc.
    const_labels = {"host": "examplehost", "app": "my_app"}

    # Create a Counter metric to track logged in users. This counter has
    # 5 separate instances.
    # We'll make use of the optional const_labels argument to add extra
    # constant labels.
    # We will also add a timestamp to the metric instances.
    # We will request that the labels be sorted.
    cm = pmp.create_counter(
        "logged_users_total",
        "Logged users in the application.",
        (
            ({"country": "sp", "device": "desktop"}, 520),
            ({"country": "us", "device": "mobile"}, 654),
            ({"country": "uk", "device": "desktop"}, 1001),
            ({"country": "de", "device": "desktop"}, 995),
            ({"country": "zh", "device": "desktop"}, 520),
        ),
        timestamp=True,
        const_labels=const_labels,
        ordered=True,
    )

    # Create a Gauge metric, similar to the counter above.
    gm = pmp.create_gauge(
        "logged_users_total",
        "Logged users in the application.",
        (
            ({"country": "sp", "device": "desktop"}, 520),
            ({"country": "us", "device": "mobile"}, 654),
            ({"country": "uk", "device": "desktop"}, 1001),
            ({"country": "de", "device": "desktop"}, 995),
            ({"country": "zh", "device": "desktop"}, 520),
        ),
        timestamp=True,
        const_labels=const_labels,
        ordered=True,
    )

    # Now lets create a Summary and Histogram metric object. These forms
    # of metrics are slightly more complicated.
    #
    # Remember, the collection of metrics and the management of Summary
    # Quantiles and Histogram Buckets are outside the scope of
    # functionality provided by this package.
    #
    # The following examples assume they are taking the data values from
    # a management library that can also emit the sum and count fields
    # expected for both Summary and Histogram metrics.

    # Create a Summary metric. The values for a summary are slightly
    # different to a Counter or Gauge. They are composed of a dict representing
    # the various quantile values of the metric. The count and sum are
    # expected to be present in this dict.
    sm = pmp.create_summary(
        "request_payload_size_bytes",
        "Request payload size in bytes.",
        (
            ({"route": "/"}, {0.5: 4.0, 0.9: 5.2, 0.99: 5.2, "sum": 25.2, "count": 4}),
            (
                {"route": "/data"},
                {0.5: 4.0, 0.9: 5.2, 0.99: 5.2, "sum": 25.2, "count": 4},
            ),
        ),
        timestamp=True,
        const_labels=const_labels,
        ordered=True,
    )

    # Create a Histogram metric. The values for a histogram are slightly
    # different to a Counter or Gauge. They are composed of a dict representing
    # the various bucket values of the metric. The cumulative count and sum
    # values are expected to be present in this dict.
    #
    # Libraries manageing buckets typically have add a POS_INF upper bound to
    # catch values beyond the largest bucket bound. Simulate this behavior in
    # the data below.
    POS_INF = float("inf")

    hm = pmp.create_histogram(
        "request_latency_seconds",
        "Request latency in seconds.",
        (
            (
                {"route": "/"},
                {5.0: 3, 10.0: 2, 15.0: 1, POS_INF: 0, "count": 6, "sum": 46.0},
            ),
            (
                {"route": "/data"},
                {5.0: 3, 10.0: 2, 15.0: 1, POS_INF: 0, "count": 6, "sum": 46.0},
            ),
        ),
        timestamp=True,
        const_labels=const_labels,
        ordered=True,
    )

    # Serialize a sequence of metrics into a payload suitable for network
    # transmission.
    input_metrics = (cm, gm, sm, hm)
    payload = pmp.encode(*input_metrics)
    assert isinstance(payload, bytes)

    # De-serialize the payload into a sequence of MetricsFamily objects.
    recovered_metrics = pmp.decode(payload)

    # Confirm that the round trip re-produced the same number of metrics
    # and that the metrics are identical.
    assert len(recovered_metrics) == len(input_metrics)
    for recovered_metric, input_metric in zip(recovered_metrics, input_metrics):
        assert recovered_metric == input_metric

    for metric in input_metrics:
        print(metric)


if __name__ == "__main__":
    main()

If you simply want to access the Prometheus Protocol Buffer objects directly and generate instances yourself simply import them from the package as follows:

from prometheus_metrics_proto import (
    COUNTER,
    GAUGE,
    SUMMARY,
    HISTOGRAM,
    Bucket,
    Counter,
    Gauge,
    Histogram,
    LabelPair,
    Metric,
    MetricFamily,
    Summary,
    Quantile)

License

This project is released under the MIT license.

Background

Creating metrics that can be ingested by Prometheus is relatively simple, but does require knowledge of how they are composed.

The Prometheus server expects to ingest MetricsFamily objects when it scrapes an endpoint exposing Protocol Buffer format data.

A MetricFamily object is a container that holds the metric name, a help string and Metric objects. Each MetricFamily within the same exposition must have a unique name.

A Metric object is a container for a single instance of a specific metric type. Valid metric types are Counter, Gauge, Histogram and Summary. Each Metric within the same MetricFamily must have a unique set of LabelPair fields. This is commonly referred to as multi-dimensional metrics.

Development

Get the source

$ git clone git@github.com:claws/prometheus_metrics_proto.git
$ cd prometheus_metrics_proto

Setup

The best way to work on prometheus_metrics_proto is to create a virtual env. This isolates your work from other project's dependencies and ensures that any commands are pointing at the correct tools.

You may need to explicitly specify which Python to use if you have multiple Python's available on your system (e.g. python3, python3.8).

$ python3 -m venv venv --prompt pmp
$ source venv/bin/activate
(pmp) $
(pmp) $ pip install pip --upgrade

The following steps assume you are operating in a virtual environment.

To exit the virtual environment simply type deactivate.

Install Development Environment

Rules in the convenience Makefile depend on the development dependencies being installed. Install the developmental dependencies using pip. Then install the prometheus_metrics_proto package (and its normal dependencies) in a way that allows you to edit the code after it is installed so that any changes take effect immediately.

(pmp) $ pip install -r requirements.dev.txt
(pmp) $ pip install -e .

Familiarise yourself with the convenience Makefile rules by running make without any rule specified.

$ make

Code Style

This project uses the Black code style formatter for consistent code style. A Makefile convenience rule is available to apply code style compliance.

(pmp) $ make style

Test

The easiest method to run all of the unit tests is to run the make test rule from the top level directory. This runs the standard library unittest tool which discovers all the unit tests and runs them.

(pmp) $ make test

or

(pmp) $ make test-verbose

Coverage

A Makefile convenience rule is available to check how much of the code is covered by tests.

(pmp) $ make coverage

The test code coverage report can be found here <htmlcov/index.html>_

Regenerate

The project has placed the code stub (prometheus_metrics_pb2.py), generated by the Google Protocol Buffers code generation tool, under source control.

If this file needs to be regenerated in the future use the following procedure:

(pmp) $ make regenerate

Release Process

The following steps are used to make a new software release:

  • Ensure that the version label in __init__.py is updated.

  • Create the distribution. This project produces an artefact called a pure Python wheel. Only Python3 is supported by this package.

    (pmp) $ make dist
    
  • Test distribution. This involves creating a virtual environment, installing the distribution in it and running the tests. These steps have been captured for convenience in a Makefile rule.

    (pmp) $ make dist-test
    
  • Upload to PyPI.

    (pmp) $ make dist-upload
    
  • Create and push a repo tag to Github.

    git tag YY.MM.MICRO -m "A meaningful release tag comment"
    git tag  # check release tag is in list
    git push --tags origin master
    

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